1. Field of the Invention
The present invention relates to an ink jet recording apparatus, and more particularly to a structure of the ink jet recording apparatus in which a recording liquid, generally called "ink", is ejected in the form of droplets from orifices connecting to a chamber containing said ink and at least a part of said droplets is deposited onto a recording material to perform desired recording.
Among the non-impact recording systems recently attracting attention because of negligibly low noise generation at the recording operation in contrast to the impact recording systems as exemplified by the typewriter, the ink jet recording method is recognized as particularly promising because of the possibility of high-speed recording on plain paper without any particular fixing step. In the field of ink jet recording there have been proposed various systems, some of which have been developed to commerical use while some others are still in the course of technical improvement.
In general the ink jet recording method performs the recording by ejecting droplets of a recording liquid, called ink, from minute orifices and depositing said droplets onto a recording material, and can be classified into several systems according to the method of generating such droplets and the method of controlling the flight direction of thus generated droplets.
2. Description of the Prior Art
In the following briefly explained are the representative systems of the ink jet recording.
A first system, called Teletype system disclosed in the U.S. Pat. No. 3,060,429, utilizes electrostatic attraction for generating a liquid flow which is directly deposited onto the recording material or of which flight direction is controlled by an electric field thereby causing deposition of liquid droplets onto the recording material.
A second system, such as for example Sweet system disclosed in the U.S. Pat. No. 3,596,275, and Lewis and Brown system proposed in the U.S. Pat. No. 3,298,030, utilizes a continuous vibration method to generate a flow of liquid droplets of a controlled charge, which are made to fly across a uniform electric field applied between deflecting electrodes to perform recording on the recording material.
A third system, such as for example Hertz system disclosed in the U.S. Pat. No. 3,416,153, utilizes a continuous vibration method to form and atomize liquid droplets in an electric field applied between the nozzle and annular charging electrode. In this system the strength of said electric field is modulated according to the recording signal, whereby the atomization of the droplets are controlled to obtain a tonal rendition in the recorded image.
A fourth system, such as for example Stemme system disclosed in the U.S. Pat. No. 3,747,120, is basically different form the foregoing three systems in that a piezo-vibration element provided in a recording head having a recording liquid-ejecting orifice converts electric recording signals into mechanical vibration, whereby the droplets are ejected from the orifice when needed and deposited on the recording material to perform the recording.
In addition to the foregoing, there was proposed another novel ink jet recording system which, as disclosed in the preceding Japanese Patent Application Sho No. 52-118798 (corresponding to U.S. Ser. No. 948,236 Oct. 3, 1978) of the present applicant, is different in basic principle from the aforementioned four systems. In summary said novel system is based on applying a thermal signal to the recording liquid introduced in a liquid chamber to eject said liquid in the form of droplets from an orifice connected to said liquid chamber in accordance with a force caused by the state change of said liquid and depositing said droplets onto the recording material to perform recording.
The major technical problems encountered in the foregoing ink jet recording systems can be summarized in the following four points.
The first of such problems is to achieve droplet ejection with secure response even to a high-frequency input signal and to continuously form droplets of a substantially uniform size, in order to prevent omissions or quality deterioration in the printing at the time of the high-speed recording.
The second is to achieve and maintain stable ejection of droplets within a short period when the recording operation is restarted after a pause, thus assuring high-quality recording without omission or aberration in the printing immediately from the start of a recording operation.
The third is to prevent eventual clogging, by the impurities present in the ink or by the dried ink, of the very minute ink-ejection orifices used in the ink jet recording apparatus. The solution to this problem is essential in the ink jet recording as the apparatus is disabled entirely by such clogging.
The fourth is to prevent, in case of a multiple orifice apparatus, collision or fusion of neighboring droplets during the flight thereof. In a multi-orifice system wherein plural orifices are arranged with a high density, for example 8 to 16 orifices per millimeter, plural neighboring ink droplets tend to collide and fuse together during the flight, thus resulting in unevenly sized droplets or distorted deposition on the recording material, thus deteriorating the printing.
In the field of ink jet recording there has not been proposed a technology capable of completely solving all the foregoing technical problems.